1. Field of the Invention
This invention relates generally to wireless telecommunication. More particularly, it relates to location roaming in CDMA, GSM, IMS/LTE, SUPL, etc. environments.
2. Background of the Related Art
Conventional wireless devices typically contain multiple cellular radios to support roaming onto different networks, e.g., Code Division Multiple Access (CDMA) networks, Global System for Mobile Communications (GSM) networks, Long Term Evolution (LTE)/IP Multimedia Systems (IMS) networks, Wi-Fi, Secure User Plane Location (SUPL), etc. A wireless device is roaming when operating on a network other than the device's home/direct network.
Conventional 3rd Generation Partnership Project (3GPP) standards use a Roaming Location Protocol (RLP), developed by an Open Mobile Alliance (OMA) standards body, to support location determination of roaming subscriber devices. A Roaming Location Protocol (RLP) is an inter-location server protocol over which location servers exchange positioning data for devices roaming on a visited network.
FIG. 4 depicts a conventional implementation of the Roaming Location Protocol (RLP).
As portrayed in FIG. 4, a home location server (H-LS) 400 and a serving location server (S-LS) 420 (i.e. a location server currently serving a roaming subscriber device) exchange positioning data for a roaming subscriber device via Roaming Location Protocol (RLP) 410 messages.
Location servers supported within the Roaming Location Protocol (RLP) include Gateway Mobile Location Centers (GMLC) (i.e. GSM location servers) SUPL Location Platforms (SLP) (i.e. SUPL location servers), and Mobile Positioning Centers (MPC) (i.e. CDMA location servers).
The 3rd Generation Partnership Project (3GPP) specifically adopted the Roaming Location Protocol (RLP) to provide roaming location support within Secure User Plane Location (SUPL) and Global System for Mobile Communications (GSM) technologies. The Roaming Location Protocol (RLP) also provides roaming location support for Code Division Multiple Access (CDMA) technologies (CDMA support is introduced in RLP 1.1). However, CDMA standards do not yet support the Roaming Location Protocol (RLP).
Unfortunately, several issues arise when attempting to use the Roaming Location Protocol (RLP) as specified within 3GPP standards and as proposed for CDMA. For instance, conventional implementations of the Roaming Location Protocol (RLP) do not provide location heterogeneity. In particular, the Roaming Location Protocol (RLP) does not directly support location determination for subscriber devices roaming on a visited carrier network (i.e. any carrier network that differs from a device's home/direct carrier network). Hence, positioning data is not obtainable for, e.g., a U.S. CDMA carrier device roaming on a European GSM network.
Moreover, the Roaming Location Protocol (RLP) relies on a mesh network of interconnected location servers.
FIG. 5 depicts an exemplary mesh network of location servers.
As depicted in FIG. 5, conventional 3GPP standards require a location server to know about and maintain connectivity to all other location servers in a roaming ecosystem. This requirement results in an expensive and impractical mesh network 510 of location servers 500a-500f. A mesh network 510 of location servers 500a-500f increases a network carrier's vulnerabilities, as it introduces multiple ingress/egress points in to a network. Multiple ingress/egress points in a network also presents cost and risk issues, since each ingress/egress point must be maintained, monitored, and controlled.
The Roaming Location Protocol (RLP), as defined for GSM and SUPL, requires an expensive mesh network 510 of location servers 500a-500f and is therefore typically not adopted in practice. When the Roaming Location Protocol (RLP) is implemented, the solution is cost prohibitive.
An SS7 mechanism is defined for roaming location support within the CDMA control-plane. However, this SS7 mechanism is cost-prohibitive and therefore not adopted in practice.
Moreover, a proprietary solution is defined for roaming location support within the CDMA user-plane. However, this solution unfavorably requires carriers to share network descriptions with other carriers, and is therefore not adopted in practice.
Additional solutions do exist for user-plane roaming. However, adoption of these standards is lacking due in part to: partial carrier support for the user-plane, low SUPL V2.0 adoption (within which user-plane roaming is defined), undesirability of Base Station Almanac data sharing (a requirement in conventional user-plane roaming standards), and difficulty justifying a return on investment (ROI).
Additional solutions also exist for control-plane roaming. However, adoption of these standards is lacking due in part to: a lack of inter-carrier agreements, a low adoption of IS-881 roaming features (which define several location request signaling messages), a cost prohibitive LPREQ feature (an IS-41 message used to query a home location register (HLR) for the address of a serving location server (S-LS)), interoperability issues resulting from dissimilar vendor implementations, prohibitive costs of features, maintenance mappings, translations, etc., and difficulty justifying a return on investment (ROI).
Conventional roaming solutions do not provide consistent location support for CDMA networks, nor do they provide consistent location support across heterogeneous network standards.
Standard roaming solutions also fail to identify the cost disparity between coarse location and precise location fixes. A coarse location fix (typically resolved by a location server) is a relatively inexpensive activity that does not significantly tax a serving infrastructure. Alternatively, a precise location fix is expensive to a serving infrastructure, since session license costs are high. Infrastructure utilization is also considerably higher for a precise location fix, since interaction for a precise location fix stretches all the way to a target device. Failure to account for the cost disparity between coarse and precise location fixes is another factor preventing adoption of conventional location roaming solutions.